Regex `(|)` giving incorrect syntax error

[alexios-angel]

The regex (|) is incorrectly giving a syntax error in CTRE.

Regex101 link https://regex101.com/r/oEx4iN/1
Compiler explorer link https://godbolt.org/z/z7fbaTfn6

#include "ctre.hpp"

// https://regex101.com/r/oEx4iN/1

int main(){
    auto i = ctre::match<"(|)">;
    return 0;
}

The correct grammar is suppose to be:

template <size_t Index>
ctre::capture< Index, ctre::select<ctre::empty, ctre::empty> >